Imaging of childhood non-Hodgkin lymphoma: assessment by histologic subtype.

The types of childhood non-Hodgkin lymphoma (NHL) differ considerably from Hodgkin lymphoma and NHL seen in adults, both pathologically and clinically. Essential to understanding these differences is a knowledge of the three major histologic subtypes (undifferentiated, lymphoblastic, and large cell) that account for the vast majority of cases of pediatric NHL. Each of these subtypes has typical imaging and clinical features. The most common subtype, undifferentiated NHL, usually shows intraabdominal disease. Lymphoblastic tumors most frequently manifest as a mediastinal mass, perhaps with respiratory or circulatory compromise. Large cell tumors show heterogeneous clinical and imaging features but tend to spare the anterior mediastinum. Knowledge of the appropriate imaging modality to be used in evaluation of these tumors is also important. Computed tomography (CT) is the primary imaging modality for staging childhood NHL. Magnetic resonance imaging is best for examination of the central nervous system and bone involvement. Ultrasonography may be useful as a complementary study to abdominal CT; gallium scintigraphy also plays an adjunctive role to CT. Familiarity with typical and atypical patterns of tumoral behaviors and optimal imaging methods aid in the diagnosis and appropriate follow-up of these tumors.